Trucks and cabs pull trailers that often have tarp systems. Similarly, rail cars may have open top container cars for which tarp systems may be used. Tarps are well known for covering contents of a container of the trailers and railcars during transport. Roll tarps often include a tarp attached on an axle or roller to a side of a container. Tarp systems are well suited for local regulations that require a container to be covered while transporting contents of the container. But local regulations also often set side, front and corner restrictions on the envelope for the whole container with accessories.
For example, European and Australian regulations require a maximum envelope for containers of trailers. Similarly, rail cars have envelopes required to operate through tunnels and the like. This envelope includes additional accessories such as tarp systems. But containers of transfer trailers and railcars are often built for maximum volume since they typically haul light materials and will fill before they are over weight. Unfortunately, little space is left for incorporating a tarp system.
Automatic solutions for tarp operation are important as a safety and efficiency issue. One goal is to keep the trailer or railcar operators on the ground, rather than manually rolling and unrolling the tarp from a catwalk on the front of a container.
In typical powered tarp system, the motor is directly attached to the front of the axle. The motor is relatively big and bulky requiring a lot of space at the front corner to operate. The resulting geometry of such a motor may be outside the envelope defined by European or other regulations.
Multiple gearboxes, such as two 90 degree gearboxes were tried, but they still must square the corner with difficulties being in the required envelope. Also, the gears of required size cannot handle the necessary torque without reliability issues. Gear boxes used in association with corners of trailers often exceed the maximum allowable envelope for trailers.
Earlier Roll-Rite patents protect aspects of a motor and knuckle arm assembly to unroll to open and to roll to close the tarp to cover the contents of a container.
U.S. Pat. No. 6,916,060 discloses arm assembly for a cover of a truck having a base, an intermediate segment, and an extension.
U.S. Pat. No. 7,195,304 discloses roll tarp system for use on vehicles and trailers with rear doors or gates. The roll tarp system includes a tarp attached to a side of a container, a roller attached to the tarp opposite of the container, a rear inner arm pivotally attached to the container, a first bias member attached to the rear inner arm, a rear outer arm attached to the first bias member, a second bias member attached to the rear outer arm and rotatably connected to a rear end of the roller and a front support structure rotatably connected to a front end of the roller.
For jurisdictions with restrictions, suitable tarp systems must fit within envelope restrictions for an open top container.